Variable speed transmission control with an adjustable limit switch



June 22, 1954 F, LEWELLEN ETAL 2,682,025

VARIABLE SPEED TRANSMISSION CONTROL I WITH AN ADJUSTABLE LIMIT SWITCH Filed Jan. 18, '1950 3 Sheets-Sheet 1 INVENTORS EMMONS E LEWELLEN .DARCY E. LEWELLEN yw mMza-w ATTORNEYS June 22, 19 54 LEWELLEN ET AL 2,682,025 VARIABLE SPEED TRANSMISSION CONTROL WITH AN ADJUSTABLE LIMIT SWITCH Filed Jan. 18, 1950 3 Sheets-Sheet 2 aq POWER LINE VARIABLE SPEED omvs TRANSMISSION uq'roa INVENTORS IE- 6 EMMONS FTLEWELLEN DARCY E. LEWELLEN ATTORNEYS un 2 1954 E. F. LEWELLEN ET AL 2,682,025

' VARIABLESPEED TRANSMISSION CONTROL WITH AN ADJUSTABLE LIMIT SWITCH I5 Sheets-Sheet 3 Filed Jan. 18, 1950 34 36 I96 I64 I68 INVENTOR EMMONS F. LEWELLEN DARCY E. LEWELLEN- BY TIM/mm 5 ZJ'mMmI/m ATTORNEYS Patented June 22, 1954 VARIABLE SPEED TRANSMISSION CONTROL WITH AN ADJUSTABLE LIllIIT SWITCH Emmons F. Lewellen and Darcy E. Lewellen,

Columbus, Ind.

Application January 18, 1950, Serial No. 139,25

14 Claims. 1

This invention relates to variable speed transmissions, and to control devices and systems therefor.

In many machines and process apparatus, there are employed variable speed transmissions which are utilized for the purpose of obtaining control over the speed of the machines being driven. Among the many processes adapted for being carried out in machines which are benefited by being controllable in speed, are processes for treating strip metal, paper, cloth, thread, yarn, and many other materials.

In the treating of textile materials such as referred to above in long lengths, a great many work processes involve the application of liquids to the material as, for example, in the form of dye, and the subsequent drying of the material. In work cycles of this nature, the amount of moisture remaining in the material after it leaves the dryer, is best controlled by controlling the speed of movement of the material being treated.

At the same time, most materials, such as textile materials referred to, must be fed onto a spool o-r take-up reel, and the said spool or reel periodically replaced with another. In removing a filled spool, the entire process machinery is generally slowed down to its slowest speed and then stopped. Thereafter, the filled spool is removed and replaced by an empty spool and the machine is then again started at its slowest speed. When the material is well started on the spool, the machine is returned to its previous running speed.

It is desirable to be able to effect the foregoing changes in speed of the machine while still being able to return the machine automatically to some pre-selected optimum speed.

It is also of advantage to be able to adjust the optimum speed at which the machine runs, in order to compensate for differences in moisture content and the like in the material being treated.

Accordingly, one of the primary objects of this invention is the provision of a variable speed transmission having associated therewith, a control system such that the speed of operation of the transmission can readily be adjusted, but, in which a predetermined maximum speed of operation can always be had after the transmission has been slowed down.

Another objectof this invention is the-provision of a control system for a variable speed transmission in which the maximum operating speed of the transmission can readily be adjusted at any time while the speed of operation of the transmission can be adjusted at any time independently of the adjustment of the maximum.

It is still another object to provide a control system for a variable speed transmission, in which the transmission will normally operate at apredetermined speed, but which permits slowing down of the transmission to a halt and thereafter the automatic return of the transmission to the speed of operation which it had before the said slowing down.

A still further object is the provision of a control system for the variable speed transmission having upper and lower stops to predetermine the possible variation in speed of the transmission, in which the stop determining the upper limit of speed can readily be adjusted to increase or decrease the maximum speed of operation of the transmission.

These and other objects and advantages wil become more apparent upon reference to the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a plan view of a transmission constructed according to our invention;

Figure 2 is a side elevational view showing a portion of the control devices for the transmission of Figure 1, and is indicated by the line 2-2 on Figure 1;

Figure 3 is a view showing the lower end of the transmission of Figure l, and connected therewith, the electrical control circuit forming a part of this invention; and

Figures 4, 5, and 6 are partial plan, end, and partial side views, respectively, of a modified form which a control device according to our invention may take.

Referring to the drawings, the transmission shown therein comprises a frame I!) having journaled therein, a constant speed input shaft 12, and a variable speed output shaft M. Mounted on shaft I2 are the adjustable sheave parts Hi, and mounted on shaft I 4, are the corresponding adjustable sheave parts 3. A suitable transmission belt 20 drivingly interconnects the sheaves according to practices well known in the art.

The sheave parts l6 and I8 are adjustable axially of their supporting shafts by means of the levers 22 pivoted to sheave parts [8 by links 24, and to sheave parts l6 by links 26. Intermediate links 24 and 26, each of the levers 22 is pivotally connected by a link 28 with a block 36 threaded onto a rod 32. The end parts of rod 32 are oppositely threaded so that adjustment of therod will move the blocks 30 in opposite directions and thereby adjust the positions of levers 3 22 and sheave parts l6 and 18, so as to maintain belt 20 in good driving engagement with both of the said sheaves.

The lower ends of levers 22, as viewed in Figure 1, are connected by links 34 with the blocks 36 mounted on the oppositely threaded parts of screw 38 that is journaled in frame IQ. It will be evident that adjustment of screw 38 will cause one set of sheave parts to move toward each other, and the other set to move away from each other, thereby to vary the driving ratio between shafts l2 and M. Screw 38 is adjustable by being geared to a motor M, as by spur-gears 40. Motor M is reversible, and is preferably a three-phase motor, so it can readily be reversed by changing the direction of phase rotation of the electrical energy supplied thereto.

Carried on one of blocks 3'6 is a pin 42 movable between a pair of adjustable screws 44 and 46 which are associated with the actuating arms of limit switches which determine the maximum limits between which the driving ratio of the transmission can be adjusted.

The same block 3% also carries a part 48 that adjustably supports a cam 50 adapted for engagement with a limitswitch LSI which is connected in a circuit for determining a maximum speed for the output'shaft l4 ofthe transmission, less than that determined by the switch associated with adjustment screw 44.

Turning to Figure 2, it will be observed that limit switch L8! is mounted on a member 52 which is screw-threadedly engaged by a threaded rod 54 mounted in frame I and having the same thread thereon as that portion of screw 38 on which the block 36 is mounted that carries cam 50. Member 52 is preferably slidably supported on a rod 53 which also prevents rotation of the said member withthe threaded rod 54.

Threaded rod 54 is-adaptedfor being drivingly connected with screw 33 by means of the gear arrangement shown in Figure 2. In this view, itwill be seen that screw 38 has a gear 58 on the end thereof, and that threaded rod 54 has a gear fifl thereon the same size as gear 58. An idler gear 62 connects gears 58 and 60, and is mounted on one end of a bell-crank lever 64 pivoted about the axis of rod 54 and spring urged by'a spring 53 in a direction to cause the gearing to engage as shown in Figure 2. A solenoid SI is connected with lever 64 so that when the solenoid is energized, it opposes spring '66 and moves the bell-crank lever and'gear 36 into position to disengage the said gear from gear 58.

Turning again to Figure '3, the transmission is shown connected with its electrical control system. At the top of the view, the various parts illustrated are identified by legends,- and the work-cycle illustrated, is that of drying a continuous length of 1 material such as a textile fabric.

In Figure 3, the individual lines of the threephase power line, are identified as at Ll, L2 and L3; These lines are connected through the blades 1c, 12 and "M ore contactor generally indicated at 16 with the terminals of motor M for driving it in one direction. The same power lines are similarly connected,- but in reverse order, with the terminals of motor M through blades 18, 80 and 82, and a second contactor generally indicated at 84.

Associated. with contactor I6 is an auxiliary contactor 8t, and similarly associated with contactor 84, is an auxiliary contactor 88. Contactor B6 hasa blade 90 connected'between power line controlled by a blade 94 of contactor i6.

LI and one terminal of the actuating coil for contactor 76, the other terminal of which is connected with one terminal of switch LS2 associated with abutment screw 46. The other terminal of limit switch LS2 is connected with power line L2. It will be apparent that closing of contactor 86 will bring about energization of contactor 16, and that this energization will continue until contactor 86 is opened, or until switch LS2 is opened.

Contactor 86 also has a blade 92 that is connected between power line LI and one of the contacts The other contact controlled by blade 94, is connected with one terminal'or solenoid SI, the other terminal of which is connected with power line L2. It

will be apparent at this point, that whenever both of contactors l6 and 86 are closed, solenoid S! will be energized for disengaging gear 62 from gear 58, thereby interrupting the driving connection between screw 38 and threaded rod 54.

One terminal of the coil for contactor 86 is connected by a wire 96 with the movable arm of limitswitch LS2, while the othertermin'al of the said coil is connected by a wire 98 with one contact of the push-button switch lOILwhich has a second contact connectedwith power line. Ll. Turning now to contactors 84 and 33', oneterminal of the coil for contactor 34 is. connected with themovable arm of limit switch LS3 associated with the button screw 4t, while the other terminal of the coil .isconnected with one contact ofbl'adelOZ of=contactor 68, the other contactor of which is connected with power line I. Contactor 88 also has a blade I04 which has one contact connectedwvithpower line LI, and a second contact connected by wire at with one'contact 'ofnblade 1G8 of contactor 84,.the other contactor ofwhich is connectedawith the'side of solenoid SI opposite itsconnection with power line L2.

*One terminal of-the coil for contactor 88 is connected with I contact I ID of a push-button switch l 52 which has a-second contact connected with power line LI; The other terminal ofthe said coil is connected by a'wire ll4zwith one of a pair of contacts controlled by limit switch LSI. The other of this pair of contacts is connected by a wire H5 with the movable arm of limit switch LS3.

Limit switch LS! has a second pair of contacts, one of which is connected by wire I It with power line Li, and the other of which is connected by wire H8 with one contact of each of a pair of push-button switches I20 and I22. The other contact of push-button 1231s connected by wire I24 with one side of the coil of contactor 16, the other side being connected, as pointed out previously, to the movable arm of switchLS2.

The other contact of switch 122 is connected by a wire l2twith one side of the coil of contactor 84,-the otherside of which is connected with the movable armpart of switch LS3 as described above.

Limit switch LSI is normally biased by a spring I28 so as to close on the first mentioned pair of contacts and which are connected respectively, one with the movable arm of switch LS3, and the other with one end of the coil of contactor 83. When limit switch LSI is engaged by cam 50, it snaps from the position in which it is shown in Figure 3 into position to close on the other pair of contacts, and which are connected between switches 12B and "I22 and power line Ll.

It will be apparent from the foregoing, that power line L2.

switches I26 and I22 can be efiective only when limit switch LS5 is in the position in which it is actuated by cam 58, and that when cam 56 is spaced from the limit switch, the said switches I2!) and I22 are ineflective.

It will also be apparent that whenever one of contactors 86 and 88 are closed, the associated one of the contactors E8 and 84 is closed, and solenoid SI is energized, thereby leading to an adjustment of the driving ratio of the transmission, but without any adjustment of threaded rod 54.

However, whenever cam 50 is in position to actuate limit switch LSI, then switches I26 and I22 can be availed of for energizing contactors it and 84, thereby bringing about energization of motor M to adjust the driving ratio of the transmission, but without energizing solenoid Si so that threaded rod 54 rotates with screw 33 and causes limit switch LSi to move in unison with cam 59. A cycle of operations can now be described. Assuming that the transmission is operating at a certain speed, let it be further assumed that it desired to halt the transmission so that a new take-up spool can be mounted for receiving the material to be treated. For slowing down the transmission, the operator closes switch I60, thereby establishing an energizing circuit from power line LI through switch I00, wire 98, to the coil of ccntactor fit, then from the coil through wire st, to limit switch LS2 and then to power line L2. This will energize contactor 86 and close blades 98 and 92 thereof. Blade 95 will establish a circuit from power line Li to one end of the coil for contactor it, and from the other end of the said coil through limit switch LS2 to power line L2. This will bring about closing of contact-or 16, thereby connecting motor M with power lines Ll, L2 and L3 for driving motor M in a direction to reduce the speed of output shaft I4.

When contactors s5 and it closed, a circuit was also established to power line LI through blades 92 and 9t and solenoid S! to power line L2, so that the afore-mentioned energization of motor M will drive screw 38, but will not drive threaded rod 54.

Blade 92 also serves to establish a holding circuit for the coil of contactor 86, so that the con tactors will remain energized until arm 42 engages abutment screw 4t and opens limit switch LS2. When limit switch LS2 opens, the output shaft is operating at low speed, and the machine can readily be shut down when the spool therein is filled.

After the filled spool has been removed and an empty spool is placed in the machine, the drive motor for the transmission is again energized, so that the machine commences running again at its lowest speed. At this time, the material can readily be started onto the empty spool. Thereafter, the machine is speeded up by readjusting the transmission to its former operating speed by closing switch II2. Closing of switch I I2 establishes a circuit to power line LI through said switch, then through the coil for contactor 88, switch H4, the left-hand pair of contacts of limit switch LSI, and limit switch LS3 to This will close contactor 88, and blade H32 thereof, will establish an energizing circuit from power line LI through the coil of contactor 84 and limit switch LS3 to power line L2, and this will close contactor 2t and connect motor M with power lines LI, L2 and L3 in such a manner that its direction of rotation is'opposite to that which obtains by closing of contactor 1B.

The screw 38 is therefore driven in a direction to increase the speed of output shaft I4. Closing of contactors 88 and 84 also establishes a circuit through blades IM and I08 to solenoid SI, so that gear 62 is disengaged from gear 58 in the same manner previously described, and whereby rotation of screw 38 is not accompanied by any adjustment of threaded rod 54. Blade I04 and contactor 88 also establishes a holding circuit therefor, so that contactors 88 and 84 will remain energized until limit switch LSI is engaged and actuated by block 50. At this point, contactors 88 and 84 will be deenergized and adjustment of the driving ratio will halt so that it is again operating at' the same speed as it was before it was initially slowed down, as described above.

\Vhenever limit switch LSI is actuated by cam 50, a circuit is established from power line LI through wire IIB, the right-hand pair of contacts of limit switch LSI and wire I I8, to switches I20 and I22. Under these conditions, switches I 20 and I22 can be availed of for adjusting the speed of the transmission, while simultaneously adjusting the position of limit switch LSI. For example, if it is desired to slow down the transmission, then s'witch I20 is closed and establishes a circuit through wire I24 to the coil of com tactor I6. This will close contactor It, while leaving contactor 86 open. Thus, motor M will be energized to turn the screw 38 in a direction to reduce the speed of output shaft I4, but inasmuch as solenoid SI is not energized, threaded rod 54 will be driven through gears 58, BI) and 62 and cause switch LSI to move in unison with its actuating cam 50. This adjustment of the transmission can continue until limit switch LS2 is opened.

If, on the other hand, it is desired to increase the speed of the transmission, then switch I22 is closed and establishes an energizing circuit for the coil of contactor 84. This will close contactor 84 and energize motor M to run in a direction to increase the speed of output shaft I4, but inasmuch as solenoid SI is not energized, rod 5 will rotate in unison with screw 38 and cause limit switch LSI to move in unison with cam 55 This adjusting movement of the transmission can continue until the limit switch LS3 is opened.

It will now be apparent that the transmission, when running at any predetermined speed, can be slowed down to its slowest speed and halted, and thereafter automatically returned to the said predetermined speed. Also, whenever the transmission is running at said predetermined speed, a selective adjustment of that speed can be made. Thus, the transmission is normally adjustable between an upper limit determined by switch LSI, and a lower limit determined by switch LS2, while switches LS2 and LS3 determine the maximum limits of adjustment of the transmission.

Turning now to Figures 4, 5, and 6, there will be seen a modified arrangement of our control device. The portions of Figures 4, 5, and 6 which correspond with portions of Figures 1 through 3 bear corresponding numbers, and the description of these corresponding parts of the device obtains for all of the views.

In Figures 4, 5, and 6, the frame It of the transmission has an extension I52 thereon, and extending transversely of the extension parallel to screw 38 are a pair of rods I52 which slidably support a plate or platform I54, as by means of 7 the bearings [56. Plate I54 serves as a support for limit switch LSI and solenoid Si, this switch and solenoid corresponding in function to switch LS! and solenoid SI described in connection with Figures 1 through 3.

Also mounted on platform Hi l is a brake arm E53 having a brake shoe portion E60 adapted for engagement with one of rods I52. Spring IE2 normally urges brake arm I53 toward brake disengaged position, and energization of solenoid SI is adapted for urging the said brake arm into brake engaging position.

In the first modification of our control device, the support for limit switch LSi was moved in unison with one of the nuts 36 by a threaded rod selectively cngageable with screw 38. According to the form of the invention illustrated in Figures i, 5, and plate 554 is movable in unison with the right-hand one of nuts 36 by means of extension Hi4- on arm at.

This extension has an aperture i8 5 adapted for engageemnt with a part on the armature oi solenoid Si when the said solenoid is de-energiz-ed. It will be apparent at this point that when solenoid Si is de energized, plate is; is connected with righthand nut 3% for movement in unison therewith, and that when the plate and nut are so connected, brake arm l at is in dis-engaged posi tion.

However, upon energization of solenoid SI. the connection between plate I54 and right-hand nut 35 is interrupted, the brake arm i moved to brake engaged position, thereby firmly holding plate 5 3 in its adjusted position. It will be apparent that the function of solenoid Si in the modified form of this invention is the same as it has in the modification shown in Figures 1 through 3, wherein. energization of the solenoid disconnected gears 58 and 63 for independ ent movement or right-hand nut 36 and the support for LS1, while de-energisation of the said solenoid interconnected the said nut and support for movement in. unison.

In connection with the modified form of the invention, it will also be evident that, as in the case of the first modification, abutment member 56 must be in engagement with the movable arm of limit switch LS! before energization of solenoid Si can take place. Abutment 5!] and aperture H38 in extension ifi l are therefore adjusted relatively, so that when the said abutment is in position to actuate limit switch LSI, the said aperture will be aligned with part I68. of the armature of solenoid Si.

It will be understood that this invention is susceptible to modification in order to adapt it to differentusages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the of the appended claims.

We claim:

1. In a control system for a variable speed transmission; a member movable for varying the driving ratio of the transmission, a reversible motor energizable for actuating said member in its opposite directions of movement, a control element positioned for engagement by said memher in one direction of movement of the member and adapted for dmenergizing said motor when so engaged to predetermine at least one limit of adjustment of said member, means movably supporting said control element for movement in the same direction as said member, means for energizing said motor, and clutch means selectively operable for drivingly connecting said con.-

8. trol element with said member so as to move. in unison with said member to adjust the limit of adjustment of the member which is determined by said element, or for disconnecting said control element from said member to leave said limit of adjustment in a fixed position.

2. In a control system for a variable speed transmission; a member movable for varying the driving ratio of the transmission, a reversible motor energizable for actuating said member in its opposite directions of movement, an electrical control element positioned for engagement by said member and adapted for de-energizing said motor when so engaged to predetermine at least one limit of adjustment of said member, mean supporting said control element for movement in the same direction as said member, first control means operable for reversibly energizing, said motor while said control element remaining stationary, and second control means operable. for reversibly energizing s" id motor and including clutch for Chi vn ly connecting said control element with said member for causing movement of control element in unison with said member, said second control means being connected in. circuit with. said control element so as to be operatvie only while said controlele ment is engaged by said-member.

3. In a control system for an adjustable memher; first and second control elements adapted for actuation in response to said member reaching respective opposite limits of its travel operable to halt the member when so actuated, a third control element adapted for actuation in response to said member reaching an intermediate point in its travel and also operable to halt the member when so actuated, first control means operable to cause movement of said member between the limits of said first and third control elements while holding said third control element stationary, and second control means operable to cause movement of said member be tween the limits of said first and second control elements, said second control means including clutch means operable for causing said third control element to move in unison with said member, there being means supporting said third control element for movement in the same direction as said adjustable member.

4. In a control system for a variable speed transmission having drivingly connected input and. output shafts and. a member movable for varying the driving ratio between said shafts; a threaded rod. engaging said member and a reversible motor energizable for driving said rod in its opposite directions, a limit switch adapted for actuation in response to a predetermined amount of movement of said member in the direction to increase the speed of said output shaft, a second threaded rod supporting said limit switch, limit switch being in circuit with said motor for de-energizing the same when the said switch is actuated, and control means operable for energizing said motor while maintaining said rods disconnected, and for energizing said motor while drivingly connecting said rods.

5. In a control system for a variable speed transmission having drivingly connected input and output shafts and a member movable for varying the driving ratio between said shafts; a threaded rod engaging said member, a reversible motor connected with said rod, a limit switch in circuit with said motor adapted for being. actuated in response to a predetermined amount of movement of said member in the direction to increase the speed of said output ;shaft, a second threaded rod supporting said limit switch, gearing connecting said rods, first =control means for reversibly energizing said ,motor while simultaneously disengaging said gearing, second control means for reversibly energizing said motor while said gearing remains in engagement.

6 In a control system for a variable speed, transmission having drivingly connected input and output shafts and a member movable for varying the driving ratio between said shafts; a threaded rod engaging said member, a reversible motor connected with said rod, a limit switch in circuit with said motor adapted for being actuated in response to a predetermined amount of movement of said member in the direction to increase the speed of said output shaft, a second threaded rod supporting said limit switch, gearing connecting said rods, first control means for reversibly energizing said motor while simu1- taneously disengaging said gearing, second control means for reversibly energizing said motor while said gearing remains in engagement, said limit switch having normally open contacts in circuit with said second control means adapted for being closed upon actuation of said switch whereby said second control means is effective only when said switch is actuated.

'1. In a control system for a variable speed transmission of the type described having a movable member for varying the driving ratio of the transmission, and a threaded rod engaging said member; a limit switch adapted for engagement by said member for predetermining the limit of adjustment of said transmission, a secand threaded rod, supporting said switch, a gear on each rod, a movable gear adapted for meshing with the gears on said rods to drivingly conmeet the rods, and electrical means energizable for shifting said movable gear out of engagement with the gears on said rods.

8. In combination in a mechanism of the type described; a pair of threaded rods, the threads on said rods being of the same pitch, one of said rods being adapt-ed for engagement with a movable member and the other of said rods being adapted for engagement with a limit switch to be engaged by said member, a gear on each rod,

a tumbler gear normally biased into position to mesh with both of the gears on said rods, and a solenoid energizable for shifting said tumbler gear out of mesh with at least one of the gears on said rods.

9. In a variable speed transmission; a member movable for varying the driving ratio in the transmission, a reversible motor for reversibly actuating said member, limit means for predetermining at least one of the limits of movement of said member, means slidably supporting said limit means, and means selectively operable for clamping said supporting means to said member for movement in unison therewith.

10. In a variable speed transmission; a member movable for varying the driving ratio of the transmission, a reversible motor energizable for actuating said member in its opposite directions of movement, a limit switch engageable by said member for de-energizing said motor at a predetermined point of adjustment of said member to predetermine one of the limits of adjustment of said transmission, means slidably supporting said limit switch for movement in a direction substantially parallel with said member, and means :10 selectively operable for clamping said limit switch stationarily on its support or for unclamping said :limit switch from its support and clamping it instead to said member for movement in unison therewith.

, ll. Ina variable speed transmission; a member movable for varying the driving ratio of the transmission, a reversible motor encrgizable for actuating said member in its opposite directions of movement, a control element mounted for engagement by said member and adapted for deenergizing said motor when so engaged to predetermine at least one limit of adjustment of said member, first control means operable for reversibly energizing said motor while holding said control element stationary, means slidably supporting said control element for movement in a direction parallel to the movement of said member, and second control means normally clamping said control element stationarily to its support but selectively operable for reversibly energizing said motor while simultaneously unclamping said control element to permit sliding movement thereof on its support and clamping the said element to said member for movement in unison therewith, said second control means being operative only while said control element is engaged by said member.

12. In a variable speed transmission having input and output shafts and a member movable for varyin the driving ratio between said shafts, a threaded rod engaging said member, a reversible motor connected with said rod, a limit switch in circuit with said motor adapted for being actuated by said member in response to a predetermined amount of movement thereof in a direction to increase the speed of said output shaft for de energizing said motor, a plate supporting said limit switch, rods slidably supporting said plate, a brake member on said plate movable into braking engagement with one of said rods and normally urged out of brakin engagement therewith, an extension part carried by said member and extending to adjacent said plate, electrical means carried by said plate energizable for moving said brake arm into brake engaged posi-' tion and de-energizable to bring about clamping said extension part to said plate, first control means for reversibly energizing said motor while simultaneously energizin said electrical means, second control means for reversibly energizing said motor while simultaneously tie-energizing said electrical means, and said limit switch having contacts in circuit with said second control means, whereby said second control means is effective only when said switch is actuated.

13. In a control system for a variable speed transmission having a constant speed shaft and a variable speed shaft, and reversibly energizable speed changing means for changing the driving ratio between said shafts including a movable member; spaced limit means adapted for engagement by said member operable for stopping operation of speed changing means at predetermined limits of movement of said member when so engaged by the member, movably positioned limit means also adapted for engagement by said member in one direction of movement there of and also operable when so engaged to halt said speed changing means, means movably sup porting said movably positioned limit means for movement in the same direction as said movable member, means selectively operable for drivinglyconnectin said movably positioned limit means with said member for adjusting the position of References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 815,756 Sprague Mar. 20, 1906 Number 10 Number Name Date Stack Dec. 23, 1919 Godd Aug. 25, 1925 German Oct. 9, 1929 Lewellen Apr. 6, 1937 Lewellen Aug. 20, 1940 Peterson Jan. 10, 1950 FOREIGN PATENTS Country Date Germany Oct. 3, 1903 

